The field of the present invention is hydraulic pumps which are air driven.
Reciprocating air driven pumps are well known. Reference is made to U.S. Pat. Nos. 5,213,485; 5,169,296; and 4,247,264. Actuator valves using feed-back control systems are disclosed in U.S. Pat. Nos. 4,549,467 and 5,957,670. Another mechanism to drive an actuator valve is by solenoid such as disclosed in U.S. Pat. No. RE 38,239
Pumps using the above technology have been devised to increase pumping pressure. Reference is made to U.S. Pat. No. 5,927,954 which includes a power amplifier piston centered between two diaphragms.
The foregoing patents are double diaphragm pumps. Opposed piston pumps driven by an air cylinder are also known. Reference is made to U.S. Pat. No. 5,415,531. In addition to the reciprocating air cylinder driving opposed pistons, the pumping cylinders are shown to be smaller in diameter than the air cylinder in this patent. Consequently, the ratio of pressure applied to the pumped liquid relative to the air pressure driving the pump can be greater than one.
These pumps are advantageous where shop air or other convenient source of pressurized air is available for pumping. Often such a source of drive is desirable because such systems avoid components which can create sparks. Pneumatic pumps can also provide a constant source of pressure by simply being allowed to come to a stall point with the pressure left on. A pneumatic drive source capable of supply on demand is possible with such systems.
The combination of pneumatic drive with hydraulic output takes advantage of the foregoing and provides pressurized hydraulic supply. However, air driven hydraulic pumps are ancillary systems to hydraulic equipment, replacing a compact, frequently motor driven hydraulic pump. Consequently, economy of size and high power are desirable with such devices.
The disclosures of the U.S. Pat. Nos. 5,213,485; 5,169,296; 4,247,264; 4,549,467; 5,957,670; 5,927,954; RE 38,239; and 5,415,531 are incorporated herein by reference as if set forth in their entirety herein.